<template>
  <div class="pagination">
    <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo - 1)">上一页</button>
    <button v-if="startNumAndEndNum.start > 1" @click="$emit('getPageNo', 1)" :class="{active: pageNo == 1}">1</button>

    <button v-if="startNumAndEndNum.start > 2">···</button>
<!-- 中间部分，用v-for遍历数字 -->
    <button 
    v-for="(page, index) in startNumAndEndNum.end" 
    :key="index" 
    v-if="page >= startNumAndEndNum.start" 
    @click="$emit('getPageNo', page)" 
    :class="{active: pageNo == page}"
    >{{ page }}</button>

    
    <button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
    <button v-if="startNumAndEndNum.end < totalPage" @click="$emit('getPageNo', totalPage)" :class="{active: pageNo == totalPage}">{{ totalPage }}</button>
    <button :disabled="pageNo == totalPage" @click="$emit('getPageNo', pageNo + 1)">下一页</button>
    
    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>
</template>

<script>
  export default {
    name: "Pagination",
    props: ['pageNo', 'pageSize', 'total', 'continues'],
    computed: {
      // 总页数
      totalPage() {
        return Math.ceil(this.total / this.pageSize)
      },
      //计算出连续的页码的起始数字与结束数字[连续页码的数字:至少是5]
      startNumAndEndNum() {
        const { continues, pageNo, totalPage } = this
        //先定义两个变量存储起始数字与结束数字
        let start = 0, end = 0
        //连续页码数字5【就是至少五页】，如果出现不正常的现象【就是不够五页】
      //不正常现象【总页数没有连续页码多】
        if(continues > totalPage) {
          start = 1
          end = totalPage
        }else {
          //正常现象【连续页码5，但是你的总页数一定是大于5的】
        //起始数字
          start = pageNo - parseInt(continues / 2)
          //结束数字
          end = pageNo + parseInt(continues / 2)
          //把出现不正常的现象【start数字出现0|负数】纠正
          if(start < 1) {
            start = 1
            end = continues
          }
          //把出现不正常的现象[end数字大于总页码]纠正
          if(end > totalPage) {
            end = totalPage
            start = totalPage - continues + 1
          }
        }
        return {start, end}
      }
    },
    methods: {
      // 按钮点击事件

    }
  }
</script>

<style lang="less" scoped>
  .pagination {
    text-align: center;
    button {
      margin: 0 5px;
      background-color: #f4f4f5;
      color: #606266;
      outline: none;
      border-radius: 2px;
      padding: 0 4px;
      vertical-align: top;
      display: inline-block;
      font-size: 13px;
      min-width: 35.5px;
      height: 28px;
      line-height: 28px;
      cursor: pointer;
      box-sizing: border-box;
      text-align: center;
      border: 0;

      &[disabled] {
        color: #c0c4cc;
        cursor: not-allowed;
      }

      &.active {
        cursor: not-allowed;
        background-color: #409eff;
        color: #fff;
      }
    }
  }
</style>
